A guide to seedbed management

The other day a farmer from Narok narrated how he was incurring losses due to poor germination rate of his seedlings.

He said he had bought half a kilo of onion seeds at Sh12,000 and had expected to grow them on a half-acre.

However, he ended up with seeds that only fitted a quarter-acre due to low germination rate.

The rate of survival after transplanting the seedlings was also too low, with many of them dying due to the shock.

His predicament is shared by many farmers as proper seed management at the nursery poses a big challenge.

To begin with, good nursery management practices start with selecting an ideal site that is secure, with a slightly sloppy land to encourage drainage.

The site should also be near a water source for watering the seedlings. The soil should also be fertile and consider the previous crop to prevent the spread of pest and diseases.

While preparing the nursery site, consider the environmental conditions. In highlands, have a raised bed to encourage aeration and drainage while in dry areas, a sunken bed is ideal since it allows the conservation of soil moisture and prevents the seedlings from being affected by the wind.

A nursery bed should not be more than a metre in width for ease in accessing the seedlings and the number of seeds to be sowed determines the length.

The bed is prepared by clearing the land, double digging to break the hardpans and to remove the stumps and roots.

Well-rotten manure is then added at a rate of 2kg per metre square and it should then be thoroughly mixed with the soil. Levelling is then done and furrows of 2cm deep and 15-20cm apart made across the bed.

At least 1-5 grammes of seeds should be sowed per square metre to avoid overcrowding, but this depends on the crop and the variety. The seeds should be sowed singly in intervals of at least 2cm that makes an average of 50-60 seeds per furrow.

However, before sowing the seeds, the farmer should first calculate the number of seedlings he requires to avoid over or under-sowing.

For example, an onion farmer planting 60 plants per metre square on half-an-acre with effective growing surface area of 1,500 requires 90,000 seedlings.


While sowing, the farmer should consider the germination percentage and succession rate of 20 per cent hence should plant in the seedbed 108,000 seeds equivalent to approximately half-a-kilo.

The seeds should then be covered lightly and mulching done to prevent splash erosion. One should also use mulching materials from a reliable source to prevent the introduction of pests and diseases. The mulch should be seedless as seeded one would result in germination.

Watering starts immediately after applying the mulch. It should be done two times per day depending on the weather condition and the soil moisture content.

Once 70 per cent of the seeds have germinated, the mulch should be removed to prevent the seedlings from developing weak stems.

Depending on the weather conditions, you should consider erecting a shelter to protect the seedlings.

Other management practices include prevention of pests and diseases, weeding and hardening off, which is done by adjusting the watering regime.

For example, if one was watering twice per day, reduce to once. If a shelter had been erected to protect the seedlings from direct sunlight, then remove it in the morning hours and place back around noon when the temperatures are high, until the seedlings are ready for transplanting.

Hardening off is done to allow the seedlings to adapt to the environmental conditions in the open field hence reducing the transplanting shock and loss.

Seedlings are ready for transplanting after three to four weeks for sukuma wiki (collard greens), spinach, cabbages, while for onions and capsicum, they take six to eight weeks depending on the variety.

The seedling should have achieved three to four mature leaves and height of about 10-15cm apart from onions and leeks, which should also be a pencil size in thickness. During transplanting, wet the nursery bed to ensure the seedlings come off with a lump of soil.

While producing seeds for the greenhouse, use trays and soilless media such as coco peat and peat moss, which ensure you end up with seedlings that are free of soil-borne diseases.

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